药芯焊丝气体保护焊在高压Cr-Mo钢管上的应用

采用钨极惰性气体保护焊(GTAW)打底与药芯焊丝气体保护焊(FCAW)填充、盖面的焊接方法对ASME SA-335 P22和ASME SA-335 P11钢管做了焊接工艺评定。分别对其焊缝进行了拉伸、弯曲、冲击和硬度检测等力学性能试验，并通过金相照片对焊缝的微观组织进行了分析，结果证明工艺评定焊缝的各项力学性能指标都达到了ASME Ⅸ的要求，该焊接方法在实际生产中是可行的。     

Buick轿车液力变矩器上盖连接块机器人焊接

根据Buick轿车液力变矩器上盖连接块焊接特点和技术要求，采用双工位协调控制机器人焊接工作站和FCAW(药芯焊丝电弧焊)方法，解决了焊缝几何尺寸一致性、空间位置对称性、填充金属均匀性等技术问题。阐述了机器人系统配置的合理性，通过工艺试验确定了FCAW工艺参数和防止焊接缺陷的工艺措施。     

Evaluation of mass loss of weld-deposited hardfacing with cored wire Ti-FeCrC alloy

In this article, we have studied the mass loss of hardfacing applied by flux-cored arc welding. Heat input, shielding gas and number of layers of coating were changed to application of Fe–Cr–Ti–C self-shielded tubular wire. Overlapping beads were deposited on plates of carbon steel AISI 1020 to analyse the mass loss, hardness and microstructure. For the analysis of mass loss, beads were deposited forming overlapping layers of coatings. Hardness measurements were performed on the surface of the specimens of wear. A rubber wheel abrasion tester was used to access the mass loss of coatings. The coatings had retained austenite and martensite microstructure with carbides finely dispersed in the matrix. The main factors that contributed to the increase in mass loss were the cracks due to higher cooling rate of the samples deposited with low heat input, the dilution in the first layer of all samples also contributed to the increase in mass loss. The smallest mass losses were those deposited coatings with high heat input, the second and fourth layers, the samples AC2, AC4 and AS2. The volume fraction of titanium carbides contributed to the decrease in the mean free path between the particles of carbides and increased the wear resistance of the coatings.     

Sensitivity model for prediction of bead geometry in underwater wet flux cored arc welding

To investigate influence of welding parameters on weld bead geometry in underwater wet flux cored arc welding (FCAW), orthogonal experiments of underwater wet FCAW were conducted in the hyperbaric chamber at water depth from 0.2 m to 60 m and mathematical models were developed by multiple curvilinear regression method from the experimental data. Sensitivity analysis was then performed to predict the bead geometry and evaluate the influence of welding parameters. The results reveal that water depth has a greater influence on bead geometry than other welding parameters when welding at a water depth less than 10 m. At a water depth deeper than 10 m, a change in travel speed affects the bead geometry more strongly than other welding parameters.     

打底层焊道裂纹的优化检测方法

通过采用多种无损检测方法对船体焊道打底层微裂纹缺陷检出率进行对比分析和应用,从实用性和有效性两个方面确定了对焊接过程和完工后焊缝检测方法的研究和选择,最终优化了检测方法;并且消除和避免了大量裂纹类缺陷的存在,确保了焊接产品的完工质量,提高了船体的整体安全性。     

Effect of chemical composition on bead formation in TIG arc welding. Effect of chemical composition on weldability in fabrication in high alloyed steel (2nd Report)

The flux cored arc welding process has grown in use in recent times as a function of its characteristics of high rate of deposition, associated with suitable mechanical properties in the welded joint. However, many aspects still remain obscure in regard to greater utilization of this process. As a result, the intention of this work is the analysis and optimization of the voltage, wire feed speed and contact tip part distance welding parameters, in a process using tubular wire with shielding gas, on the penetration and convex index of the weld. By means of statistical techniques, a mathematical model was developed with subsequent optimization of the responses. Based on the results obtained, the strong influence of the wire feed speed on the process was seen, followed by the voltage and, with less intensity, the contact tip to workpiece distance (CTWD). Statistical analyses indicated that the best condition for the parameters analysed was obtained with voltage values between 32 and 34 V, associated with a wire feed speed of 12 m/min and a CTWD of 20 mm. On the other hand, tensions at around 36 V caused surface defects that prejudiced the quality of the weld. Later tests showed an acceptable forecast of the results of the mathematical models when compared to the actual results.     

Comparison of operational performance and bead characteristics when welding with different tubular wires

The aim of this work was to make a comparative study of the characteristics of the weld bead produced by nationally manufactured tubular wires; all rutilic (ASME SFA-5.20: E71T-1/E71T-9/E71T-9M), basic (ASME SFA-5.20: E71T-5/E71T-5M) and ‘metal cored’ (ASME SFA-5.18: E70C-3M), 1.2 mm in diameter, intended for the welding of structural steels with low and medium levels of carbon. Welding tests were carried out, in the flat position, on thick plates (with a thickness of 12 mm) of common low-carbon steel using a source operating in ‘constant voltage’ mode, with monitoring of the current and voltage signals of the arc and feed speed (fusion) of the wire. The following were varied in welding with each type of tubular wire: the composition of the shielding gas (75%Ar–25%CO₂ and 100%CO₂) and the feed speed of the wire (7 and 9 m/min). The other parameters were kept fixed, including the polarity of the electrode (DC+) and the energized lengths of the electrode (16 mm) and of the arcs (3.5 mm). For the different tubular wires, there was a comparative analysis of the principal weld bead characteristics, including its geometry (penetration, reinforcement, width, fused area, deposited area and dilution), presence of weld discontinuities, microstructure and hardness. Operational conditions that yielded weld bead characteristics that favoured the welding of thick plates of structural steels were determined.     

90°弯头内壁整体堆焊

90°弯头的内壁堆焊是加氢反应器的制造难点之一。目前通常是采取将90°弯头分为3段,各段分别堆焊后装配在一起,再对连接缝进行组焊和堆焊的制造工艺。该工艺不仅繁琐,而且质量不易控制。为了解决这个制造难题,在现有堆焊设备和焊接变位机的基础上,通过开发一些简单的辅助工装,成功实现了90°弯头的内壁整体堆焊。并详细介绍了90°弯头的制造难点、内壁整体堆焊的原理及对辅助工装的要求。     

Proposal of a New G-BOP Test to Evaluate Cracks in Weld Beads in Thin Sheets

The objective of the present work is the evaluation of a proposal for a gapped bead-on-plate (G-BOP) test, used for study of hydrogen cracks in relatively thin sheets of welded steel. That new proposal consists of the replacement of the usual solid blocks by an assembly of blocks in such a way that the test can evaluate weld beads on thin sheets. Student t distribution is applied to examine the functionality of the proposed test. Weld metals were deposited with flux-cored wires E71T-1 and E71T8-K6, with diameters of 1.6 and 1.7 mm, respectively, under two different preheating temperatures. Metal susceptibility to hydrogen cracking was evaluated by the presence and percentage of cracks in the weld metal. In order to evaluate and verify the functionality of the new G-BOP test proposal, the following were examined: efficiency of the new test in inducing hydrogen cracks in the weld metal, result replicability, fracture modes present in cracks, and the cooling rate imposed on the welding zone. Results showed that the new G-BOP test proposal is viable; results were replicable and the test was efficient in inducing cracks in weld metal with a confidence of 90%.